beta-HCG aberrant expression in primary mediastinal large B-cell lymphoma

We report on a primary mediastinal large B-cell lymphoma with aberrant expr ession of P-human chorionic gonadotropin (beta-hCG). The patient, a 33-year -old man, had cough, dyspnea, fever, superior vena cava syndrome, and a med iastinal bulky tumor. A biopsy showed that the latter was characterized by large cells, sclerosis, and compartmentalization. The neoplastic elements e xpressed CD45, CD20, CD79a and, partially, CD30, whereas they were negative for CD3, epithelial membrane antigen and cytokeratins. Surprisingly, they displayed a clear-cut positivity for beta-hCG. The remaining oncofetal mark ers applied (PLAP and alpha(1)-fetoprotein) were negative. Electron microsc opy demonstrated the presence of numerous nuclear pockets and the lack of i ntercellular junctions. DNA analysis by polymerase chain reaction showed cl onal rearrangement of Ig heavy-chain genes. The patient responded promptly to the administration of MACOP-B. To the best of our knowledge, this is the first example of B-cell lymphoma showing positivity for beta-hCG; a simila r aberrant expression was previously observed only in three Japanese patien ts with human T-cell lymphotropic virus type I+ adult T-cell lymphoma/leuke mia. Because primary mediastinal large B-cell lymphoma has in the past been frequently confused with germ cell tumors, pathologists should be aware of possible beta-hCG expression by lymphomatous cells to avoid the risk of mi sdiagnosis.